A thermal type (or uncooled type) infrared ray detection element absorbs and converts infrared rays into heat and outputs a temperature change caused by this heat as an electric signal. Thermal type infrared ray detection elements can reduce the total volume of the imaging system since a refrigerator is unnecessary. And recently the price of an infrared ray imaging device is decreasing with the aim of applying to consumer products through mounting the elements on it.
Such a background is encouraging active research and development of an infrared ray detection element that includes a silicon PN junction diode as a temperature sensing element, which can be formed within a general-purpose LSI (large scale integrated circuit) process, and that detects a temperature change of a junction current thereof.
The temperature change rate of the junction current of the silicon PN junction diode is very small as compared to, for example, that of resistance of vanadium oxide, which is also used as a temperature sensing element. Therefore, the infrared ray detection element, having a silicon PN junction diode as a temperature sensing element, has a problem of low sensitivity. Patent Document 1 describes that a sensitivity of an infrared ray detection element is improved by connecting multiple silicon PN junction diodes in series.